Display panels such as liquid crystal displays (LCDs) are commonly used in appliances such as thermostats, watches, pagers, cellular telephones, video cameras, etc. to display information. Such devices typically include a light source and light emitting panel that can be used to generate light across a surface for illuminating the display panel. In some thermostat designs, for example, the light source and light emitting panel may form part of a backlight of the display panel that can be used to facilitate viewing at night or in low-lighting conditions. Typically, the light emitting panel will include a point-type light source such as a light emitting diode (LED) or bulb adapted to direct light into a light guide, which acts as an optical waveguide to distribute the light rays across the surface of the light emitting panel. In some designs, a diffusive pattern of ridges, grooves or dots on the light emitting panel may be used to disperse the light rays in a desired pattern across surface of the light emitting panel for providing a desired lighting characteristic to the display panel.
For some designs, the light generated by the light source may be transmitted through an air gap interface disposed between the light source and the light guide. In such configuration, the uniform distribution of light within the light emitting panel is often dependent on the proper alignment of the light source relative to the light guide as well as the dimensions of the air gap. In some applications, for example, improper alignment of the light source and light guide can cause the light rays directed across the surface of the light emitting panel to be distributed non-uniformly and in a pattern different than the desired pattern. Visually, such inconsistency of light across the surface of the light emitting panel may result in hot spots or streaks on the panel, reducing the brightness and uniformity of the lighting.